Various methods have been employed for sterilization and purification of liquid. For example, UV radiation, disinfection by biocides and pasteurization have been used for water sterilization. Ultraviolet (UV) treatment has been used to disinfect clear water as described in U.S. Pat. Nos. 3,634,025; 3,700,406; 3,837,800; 3,889,123; 3,894,236; 4,471,225 and 4,602,162. Each of these U.S patents describes a method for sterilization of water-based fluids. The principal idea behind these techniques is typically that UV radiation penetrates the clear liquid to kill offending microorganisms. UV has been also used in combination with magnetic treatment (e.g. U.S. Pat. No. 5,997,812) by passing the fluid through a magnetic field followed by exposure of the fluid to a disinfecting amount of ultraviolet radiation. The conventional technology of UV treatment is limited because systems made of quartz have a tendency to foul easily and maintenance costs are high.
Another approach to disinfect water is by adding appreciable levels of various biocide fluids to kill and inhibit the growth of microorganisms (e.g. U.S. Pat. No. 3,230,137). However, people exposed to biocides may experience allergic reactions or other problems. In short, although bacterial counts can be reduced over the short term, biocides are often more problematic than the microorganisms themselves.
Another method for the disinfection of fluids is pasteurization. In this process, fluids are heated to a pasteurizing temperature for a required period of time and subsequently cooled to an operating temperature. This process is energy intensive and the costs resulting from the heating and cooling steps are high.
Various other methods for sterilization such as sterilization by ozone or H2O2 exist, however, these are either expensive, hazardous or not sufficiently effective.